1. Field of the Invention
The present invention relates to an envelope signal generating apparatus installed in, for example, an electronic musical instrument.
2. Description of the Related Art
An envelope signal generating apparatus is generally installed in an electronic musical instrument, such as an electronic organ, to multiply a tone signal by an envelope signal, providing a dynamics-added musical tone signal.
Conventional envelope signal generating apparatuses generate an envelope signal using a parameter indicating a target level and a parameter indicating a time to reach the target level. The structure to generate an envelope signal based on the target level, however, has the following shortcomings:
1) Even in phases (wave transitional phases) with the same time interval, changing the target level varies the wave generating time.
2) Every time the target level changes, it is necessary to recompute what is to be compared for discriminating whether or not the target level has been reached.
3) A small change in target level increases a computation error so that the desired waveform cannot be acquired.
The conventional envelope signal generating apparatuses manage the parameters for each envelope signal. With this design, however, the phase cannot be changed, even forcibly, during wave generation for the following reason. As the parameters are managed for each envelope signal, when phase alteration is executed, the changed phase always becomes the head phase of one envelope signal.